Display device

Abstract

There is provided an active matrix EL display device that can display a clear multi gray-scale color display to reduce the shift in the potential caused by the potential drop due to the wiring resistance of a power source supply line, in order to decrease the unevenness in a display region. A plurality of drawing out ports of the power source supply line are arranged. Further, in the wiring resistance between the external input terminal and the pixel portion power source supply line, potential compensation is performed by supplying potential to the power source supply line by a feedback amplifier. Further, in addition to above structure, the power source supply line may be arranged in a matrix.

What is claimed is: 
     
       1. A semiconductor device comprising:
 a first transistor over a substrate; 
 a second transistor over the substrate; 
 a first gate line over the substrate, the first gate line being electrically connected to a gate of the first transistor; 
 a second gate line over the substrate, the second gate line being electrically connected to a gate of the second transistor; 
 a source signal line over the first gate line and the second gate line, the source signal line being electrically connected to one of a source and a drain of the first transistor, the source signal line being electrically connected to one of a source and a drain of the second transistor; 
 an insulating film over the source signal line; 
 a wiring over the substrate, the wiring comprising a first conductive film and a second conductive film electrically connected to the first conductive film; and 
 a pixel electrode over the insulating film, 
 wherein the first conductive film, the first gate line and the second gate line comprises a same material, 
 wherein the first conductive film is positioned between the first gate line and the second gate line, 
 wherein the source signal line overlaps with the first conductive film, 
 wherein the second conductive film is over the insulating film, and 
 wherein the second conductive film overlaps with the first gate line. 
 
     
     
       2. The semiconductor device according to  claim 1 ,
 wherein the pixel electrode is electrically connected to the other of the source and the drain of the first transistor. 
 
     
     
       3. The semiconductor device according to  claim 2 , further comprising a third transistor,
 wherein the pixel electrode is electrically connected to the other of the source and the drain of the first transistor through the third transistor. 
 
     
     
       4. The semiconductor device according to  claim 1 ,
 wherein the pixel electrode is a pixel electrode of an EL element. 
 
     
     
       5. The semiconductor device according to  claim 1 ,
 wherein the first transistor and the second transistor each have a top gate structure. 
 
     
     
       6. The semiconductor device according to  claim 1 ,
 wherein the wiring is a power supply line. 
 
     
     
       7. A display device comprising:
 a first transistor over a substrate; 
 a second transistor over the substrate; 
 a first gate line over the substrate, the first gate line being electrically connected to a gate of the first transistor; 
 a second gate line over the substrate, the second gate line being electrically connected to a gate of the second transistor; 
 a source signal line over the first gate line and the second gate line, the source signal line being electrically connected to one of a source and a drain of the first transistor, the source signal line being electrically connected to one of a source and a drain of the second transistor; 
 an insulating film over the source signal line; 
 a first display element over the insulating film, the first display element being electrically connected to the other of the source and the drain of the first transistor; 
 a second display element over the insulating film, the second display element being electrically connected to the other of the source and the drain of the second transistor; and 
 a wiring over the substrate, the wiring comprising a first conductive film and a second conductive film electrically connected to the first conductive film, 
 wherein the first conductive film, the first gate line and the second gate line are formed on a same layer, 
 wherein the first conductive film is positioned between the first gate line and the second gate line, 
 wherein the first display element and the second display element are positioned between the first gate line and the second gate line, 
 wherein the source signal line overlaps with the first conductive film, 
 wherein the second conductive film is over the insulating film, and 
 wherein the second conductive film overlaps with the first gate line. 
 
     
     
       8. The display device according to  claim 7 , further comprising a third transistor and a fourth transistor,
 wherein the first display element is electrically connected to the other of the source and the drain of the first transistor through the third transistor, and 
 wherein the second display element is electrically connected to the other of the source and the drain of the second transistor through the fourth transistor. 
 
     
     
       9. The display device according to  claim 7 ,
 wherein each of the first display element and the second display element is an EL element. 
 
     
     
       10. The display device according to  claim 7 ,
 wherein the first transistor and the second transistor each have a top gate structure. 
 
     
     
       11. The display device according to  claim 7 ,
 wherein the wiring is a power supply line. 
 
     
     
       12. A personal computer comprising:
 a keyboard; and 
 a display portion comprising:
 a first transistor over a substrate; 
 a second transistor over the substrate; 
 a first gate line over the substrate, the first gate line being electrically connected to a gate of the first transistor; 
 a second gate line over the substrate, the second gate line being electrically connected to a gate of the second transistor; 
 a source signal line over the first gate line and the second gate line, the source signal line being electrically connected to one of a source and a drain of the first transistor, the source signal line being electrically connected to one of a source and a drain of the second transistor; 
 an insulating film over the source signal line; 
 a first display element over the insulating film, the first display element being electrically connected to the other of the source and the drain of the first transistor; 
 a second display element over the insulating film, the second display element being electrically connected to the other of the source and the drain of the second transistor; and 
 a wiring over the substrate, the wiring comprising a first conductive film and a second conductive film electrically connected to the first conductive film, 
 
 wherein the first conductive film, the first gate line and the second gate line are formed on a same layer, 
 wherein the first conductive film is positioned between the first gate line and the second gate line, 
 wherein the first display element and the second display element are positioned between the first gate line and the second gate line, 
 wherein the source signal line overlaps with the first conductive film, 
 wherein the second conductive film is over the insulating film, and 
 wherein the second conductive film overlaps with the first gate line. 
 
     
     
       13. The personal computer according to  claim 12 , further comprising a third transistor and a fourth transistor,
 wherein the first display element is electrically connected to the other of the source and the drain of the first transistor through the third transistor, and 
 wherein the second display element is electrically connected to the other of the source and the drain of the second transistor through the fourth transistor. 
 
     
     
       14. The personal computer according to  claim 12 ,
 wherein each of the first display element and the second display element is an EL element. 
 
     
     
       15. The personal computer according to  claim 12 ,
 wherein the first transistor and the second transistor each have a top gate structure. 
 
     
     
       16. The personal computer according to  claim 12 ,
 wherein the wiring is a power supply line. 
 
     
     
       17. An electronic equipment comprising:
 a battery; and 
 a display portion comprising:
 a first transistor over a substrate; 
 a second transistor over the substrate; 
 a first gate line over the substrate, the first gate line being electrically connected to a gate of the first transistor; 
 a second gate line over the substrate, the second gate line being electrically connected to a gate of the second transistor; 
 a source signal line over the first gate line and the second gate line, the source signal line being electrically connected to one of a source and a drain of the first transistor, the source signal line being electrically connected to one of a source and a drain of the second transistor; 
 an insulating film over the source signal line; 
 a first display element over the insulating film, the first display element being electrically connected to the other of the source and the drain of the first transistor; 
 a second display element over the insulating film, the second display element being electrically connected to the other of the source and the drain of the second transistor; and 
 a wiring over the substrate, the wiring comprising a first conductive film and a second conductive film electrically connected to the first conductive film, 
 
 wherein the first conductive film, the first gate line and the second gate line are formed on a same layer, 
 wherein the first conductive film is positioned between the first gate line and the second gate line, 
 wherein the first display element and the second display element are positioned between the first gate line and the second gate line, 
 wherein the source signal line overlaps with the first conductive film, 
 wherein the second conductive film is over the insulating film, and 
 wherein the second conductive film overlaps with the first gate line. 
 
     
     
       18. The electronic equipment according to  claim 17 ,
 wherein the electronic equipment is a video camera. 
 
     
     
       19. The electronic equipment according to  claim 17 , further comprising a third transistor and a fourth transistor,
 wherein the first display element is electrically connected to the other of the source and the drain of the first transistor through the third transistor, and 
 wherein the second display element is electrically connected to the other of the source and the drain of the second transistor through the fourth transistor. 
 
     
     
       20. The electronic equipment according to  claim 17 ,
 wherein each of the first display element and the second display element is an EL element. 
 
     
     
       21. The electronic equipment according to  claim 17 ,
 wherein the first transistor and the second transistor each have a top gate structure. 
 
     
     
       22. The electronic equipment according to  claim 17 ,
 wherein the wiring is a power supply line.